buy an evaporative humidifier - those don't coat things with a layer of white dust. Unfortunately, these are the type you have to replace a wick over time.
if you use bacteriostatic additive and demineralized water, the wicks can last a long time.
Being too cold does not make a humidifier ineffective. Well i guess if your drying room is below freezing, that's a problem, but the buds would freeze, too, lol. In fact, it's easier to maintain ~60% humidity in colder temps than warmer temps. There's no way to circumvent it. Temp and RH = drying time. either raise the humidity or continue to dry too fast.